Microwave circuits are employed for coupling electromagnetic energy between microwave components such as radiating elements including apertures, horns, circulators, signal generators and receivers. The conduits by which the electromagnetic energy is coupled between the microwave components may be constructed in various forms of transmission lines ranging from stripline and microstrip to waveguide, and frequently include various forms of power couplers, power splitters, and power combiners. Such conduits allow microwave signals to be split among a number of microwave components, and also allow the combining of signals from a plurality of microwave components.
Of particular interest herein are complex microwave circuits employing transmission lines comprising two electrical conductors for interconnecting numerous microwave components. Such circuitry is found, by way of example, in large antenna arrays employing many horn radiators, slotted arrays, and in-plane radiators coupled by signal combiners and or splitters to produce a desired radiation pattern. A Butler matrix is an example of such microwave circuitry. Typical two-conductor transmission lines are microstrip and coaxial transmission lines. In such complex microwave structures, it is frequently necessary to bring signals from various parts of the structure to other parts of the structure by waveguide paths which cross over each other. Such crossings of signals have been accomplished by bending one coaxial line about another, or by providing a multiple layer microstrip structure for passing one transmission line about another.
A problem arises in that the physical complexity and size of a microwave structure is increased by signal crossovers employing a passage of one coaxial cable or microstrip transmission line waveguide about another. It is recognized that the most simple form of such structure is attained by placing all components and connecting transmission lines in a single plane. However, heretofore, such a simplified structure has not been attainable because a multiplicity of crossover structures comprising bent coaxial lines and/or undulating microstrip lines can produce a considerable amount of stacking of the transmission lines, one above the other. Such a mechanical configuration is both bulky and heavy. Excessive bulk and weight are characterics which are to be avoided in the construction of antenna arrays, such as those employed in satellites, wherein a reduction in space and weight is most desirable.